Avoid showing the supervised user block interstitial more than once

chrome/browser/supervised_user/supervised_user_navigation_observer.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_NAVIGATION_OBSERVER_H_
 #define CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_NAVIGATION_OBSERVER_H_
 
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 36 matching lines @@
       content::NavigationHandle* navigation_handle) override;
 
   // SupervisedUserServiceObserver implementation.
   void OnURLFilterChanged() override;
 
  private:
   friend class content::WebContentsUserData<SupervisedUserNavigationObserver>;
 
   explicit SupervisedUserNavigationObserver(content::WebContents* web_contents);
 
-  void OnRequestBlockedInternal(const GURL& url);
+  void OnRequestBlockedInternal(
+      const GURL& url,
+      supervised_user_error_page::FilteringBehaviorReason reason,
+      const base::Callback<void(bool)>& callback);
 
   void URLFilterCheckCallback(
       const GURL& url,
       SupervisedUserURLFilter::FilteringBehavior behavior,
       supervised_user_error_page::FilteringBehaviorReason reason,
       bool uncertain);
 
+  void MaybeShowInterstitial(
+      const GURL& url,
+      supervised_user_error_page::FilteringBehaviorReason reason,
+      bool initial_page_load,
+      const base::Callback<void(bool)>& callback);
+
+  void OnInterstitialResult(const base::Callback<void(bool)>& callback,
+                            bool result);
+
   // Owned by SupervisedUserService.
   const SupervisedUserURLFilter* url_filter_;
 
   // Owned by SupervisedUserServiceFactory (lifetime of Profile).
   SupervisedUserService* supervised_user_service_;
 
+  bool is_showing_interstitial_ = false;
+
   std::vector<std::unique_ptr<const sessions::SerializedNavigationEntry>>
       blocked_navigations_;
 
   base::WeakPtrFactory<SupervisedUserNavigationObserver> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SupervisedUserNavigationObserver);
 };
 
 #endif  // CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_NAVIGATION_OBSERVER_H_